This invention relates generally to video peaking systems and particularly to video peaking systems for use in wide band high definition television systems. Peaking systems for television video signals are notoriously old in the art. Commonly, peaking of a video signal involves enhancing the horizontal and/or vertical transitions or edges of the video image to provide a sharper display. To avoid the peaking of noise and noise components, the video signal may be applied to a so-called "coring" circuit, which removes the noise prior to peaking of the video signal. While noise coring circuits do provide enhanced peaking performance, coring is a relatively coarse technique and is somewhat deficient in results produced.
In the HDTV video system described in the above-mentioned copending application Ser. No. 539,770, a 36 MHz wide band video signal is compressed for transmission in a standard 6 MHz television band. This is generally accomplished by transform coding successive blocks of the image signal, processing the transform coefficients generated for each block and applying them to an image classifier, where the coefficients are grouped or classified according to their perceptual nature or image type. The image classifications may generally include a boundary, edge, texture, flat video and low AC or a combination thereof. The derived classification is then used to control the level of compression effected for each respective block. The foregoing technique is clearly set forth in the above-mentioned copending application Ser. No. 539,770 and will not be further elaborated upon here.
Copending application Ser. No. 653,560 is directed to a video compression scheme that improves quantization efficiency by controlling coefficient resolution as a function of the perceptual characteristic of the video image. A system for perceptually modelling a video image signal to enhance its compressibility is shown.
The present invention goes beyond that of copending application Ser. No. 539,770 by developing a control signal (in the preferred embodiment, two control signals are developed) which reflects the perceptual nature of the video image and using the control signal to control peaking of the video signal. The invention may advantageously employ the perceptual modelling system of Ser. No. 653,560. The control signal may be used in the transmitter to control the level of the peaking component applied to the transmitted video signal or may be transmitted, along with the unpeaked video signal, to a receiver where the control signal is recovered and used to control peaking of the video signal in the receiver.